• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.431-433
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• 2007

The drawbeads, which is used for controlling the flow of the sheet by imposing the tension and for preventing the springback in the sheet metal forming process, affects a lot the formability because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining and opening forces was manufactured and the drawing forces of circular, square, and step drawbeads are measured. The drawbead restraining and opening forces of a circular drawbead are increased as its drawbead height is increased. Similarly, those of a square drawbead are increased as its height is increased and shoulder radii decreased. Also, those of a step drawbead are increased as its height and difference in their heights are increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.350-359
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• 2005

Finite element method is a very effective method to simulate the forming processes with good prediction of the deformation behaviour. For the finite element modeling of sheet mental forming the accurate die model is required. Among finite element method, the static-implicit finite element method is applied effectively to analyze real-size auto-body panel stamping processes, which include the forming stage. This study is about analyzing the stamping process problems by using AutoForm commercial software which used static-implicit method. According to this study, the results of simulation will give engineers good information to access the die design of optimization.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.06a
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• pp.79-86
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• 1994

스템핑용 냉연강판의 기계적 성질은 온도에 따라 변하므로 금형재의 열적 특성은 성형의 성공여부에 영향을 미칠 수 있으며 재질선정에 있어 중요한 인자의 하나이다. 금형재질이 성형에 미치는 영향을 조사하기 위하여 차체의 패널용으로 사용되는 강판에 대하여 상온 및 고온에서의 인장시험을 하였으며 구상흑연주철과 회주철을 중심으로 열특성을 조사하였다. 연신율과 인장 강도의 온도 의존성에 대한 검토와 함께 금형재료에 따른 열전달 특성을 분석하여 열특성 측면에서는 회주철이 구상흑연 주철보다 더 적합 하며 열전도율이나 비열 등의 열특성치도 금형재 선정에 중요한 인자중 하나라는 결론을 얻었다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1410-1413
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• 2004

Finite element method is very effective method to simulate the forming processes with good prediction of the deformation behaviour. For the finite element modeling of sheet mental forming the accurate tool model is required. Due to the geometrical complexity of real-size part stamping tools it is hard to make FE model for real-size auto-body stamping parts. In this paper, it was focussed on the drawability factors on auto-body panel stamping by AUTOFORM with using tool planning alloy to reduce law price as well as high precision from Design Optimization of die. According to this study, the results of simulation will give engineers good information to access the Design Optimization of die.

• Journal of the korean Society of Automotive Engineers
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• v.19 no.1
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• pp.3-10
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• 1997

합체 박판을 사용한 생산 방식은 소수의 스템핑 금형 공정으로 인해 전반적으로 공기가 짧아지고, 보다 견고하며 외관상 우수한 차체를 생산할 수 있다. 또한 재료의 수율을 극대화할 수 있을 뿐만 아니라 차체 각부에서 요구되는 성질과 조건에 따라 판 두께나 재질을 대응할 수 있다는 등의 장점을 가지고 있어 초기긔 설비비는 다른 생산 방식에 비해 고가이지만 전체 공정과 장기적인 관점에서 생산비가 절감된다. 본 기고에서는 합체 박판의 생산 및 활용정도와 각 기업체나 연구소들에서의 연구 진척상황, 그리고 앞으로의 전망에 대해 논한다.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.3
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• pp.96-110
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• 1993

A procedure has been developed so that a die-face for stamping automobile outer panels can be design and modelled efficiently. The procedure is composed of four parts each of which corresponds to modeling major components of a die-face, i.e. tipped product, blankholder, draw beads, and step draw. The modeling techniques developed specifically for die-face design enable a designer to generate the shape of a die-face quickly with the minimum input, and the resulting models can be used in FEM analysis and NC tool path generation. This will lead to the reductions in lead time and manhours required for the design and manufacture of the stamping dies.

• Transactions of Materials Processing
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• v.20 no.6
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• pp.427-431
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• 2011

In general, hot stamped component is trimmed by costly and time consuming laser cutting when the material strength is over 1,500MPa. The aim of this work was to demonstrate that the trimming die life is improved and the trimming load is decreased by lowering the strength of the region to be trimmed. The model employed in this study was a hat shape, similar to the cross section of many hot stamped products. FE-analysis of hot stamping process was performed to evaluate the effect of tool shape on cooling rate at the area to be trimmed. The best tool shape was thus identified, which created slower cooling and lower hardness at the region to be trimmed. The wear at the cutting tool edge was also reduced.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.457-462
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• 2007

The drawbeads, which are used for controlling the flow of the sheet into die cavity by imposing the tension and for preventing the forming defects like wrinkling, springback, etc. during the sheet forming process, affect the formability strongly because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining and opening forces is manufactured and the drawing forces of circular, square, and step drawbeads are measured. The drawbead restraining and opening forces of a circular drawbead are increased as its drawbead height is increased. Similarly, those of a square drawbead are increased as its height is increased and shoulder radii decreased. The drawbead forces obtained from the experiment were compared with those calculated in the numerical simulation of stamping process of automotive fender. Good agreement was found so that the experimental measurements can be used in the simulation of auto-body stamping process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.658-666
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• 1992

In developing computer-aided design technology for optimization of stamping die design, it has been an important issue to treat the frictional constraint acting on the blank holder surface. The main goal of this work is to establish database of draw bead restraint force and clarify friction characteristic for various automotive sheet steels, which is essential in developing friction algorithm that can be used for CAD of stamping die design. Draw bead friction tester is used to evaluate the various parameters that affect the draw restraint force and the coefficient of friction for the cold rolled and the coated sheet steels such as drawing rate, lubricant type, surface property of material, etc.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.10-18
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• 2008

Metal stamping is widely used in the mass-production process of the automobile industry. During the stamping process, air may be trapped between the draw die and the panel. The high pressure of trapped air induces imperfections on the panel surface and creates a situation where an extremely high tonnage of punch is required. To prevent these problems, many air ventilation holes are drilled through the draw die and the punch. The present work has developed a simplified mathematical formulation for computing the pressure of the air pocket based on the ideal gas law and isentropic relation. The pressure of the air pocket was compared to the results by the commercial CFD code, Fluent, and experiments. The present work also used the Bisection method to calculate the optimum cross-sectional area of the air ventilation holes, which did not make the pressure of the air pocket exceed the prescribed maximum value.